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Conversions  B Units of Measurement | Metric & SI Prefixes | Conversion Factors Units of Measurement The metric system is used by scientists and health professionals worldwide.  A modified version of metric, called the International System of Units (SI) was adopted in 1960 to provide additional uniformity.  The table below notes common units of measurement in both metric and SI:

 UNITS OF MEASUREMENT Measurement Metric SI Length Meter (m) Meter (m) Volume Liter (L) Cubic Meter (m3) Mass Gram (g) Kilogram (kg) Time Second (s) Second (s) Temperature Celsius (0C) Kelvin (K) Length, time and temperature are fairly self-explanatory.  Volume and mass need a little more clarification.  Volume measures the amount of space occupied by a substance. Think of volume as a fluid measurement, such as how much water is in a glass.  Mass is a measure of the quantity of material an object contains.  It may be helpful to think of mass as a measurement of weight, such as the weight of a patient. It should be noted, however, that mass is not the same as weight.  Weight is the measure of gravitational pull on an object.  In space, a man will weigh less than on earth but the man's mass will not change.  That is why scientists measure mass instead of weight - mass does not vary. Metric and SI Prefixes In both metric and SI, a prefix can be attached to any unit to increase or decrease its size by some factor of 10.  For example, a kilogram is equal to 1,000 grams; a milligram is equal to one-thousandth of a gram.  The table below illustrates this unique feature:

 METRIC AND SI PREFIXES Prefix Symbol Meaning Numerical Value Scientific Notation Prefixes that increase the size of a unit mega M one million 1,000,000 106 kilo k one thousand 1,000 103 Prefixes that decrease the size of a unit deci d one-tenth 0.1 10-1 centi c one-hundredth 0.01 10-2 milli m one-thousandth 0.001 10-3 micro m one-millionth 0.000001 10-6 nano n one-billionth 0.000000001 10-9  Conversion Factors In the healthcare field, you will make changes in units everyday.  For example, you may need to convert someone's weight in pounds to their weight in kilograms to calculate a proper dosage for the patient's size.  Conversion factors are simple formulas that help you do this.  The first table below lists measurement equivalents.  The second table lists metric conversion factors and the third table lists metric-to-U.S. relationships and conversion factors.

 MEASUREMENT EQUIVALENTS Length 1 meter (m) = 100 centimeters (cm) 1 meter (m) = 1000 millimeters (mm) 1 meter (m) = 39.4 inches (in.) 1 inch (in.) = 2.54 centimeters (cm) Volume 1 liter (L) = 1000 milliliters (mL) = 1000 cm3 1 liter (L) = 1.06 quarts (qt) 1 quart (qt) = 946 milliliters (mL) Mass 1 kilogram (kg) = 1000 grams (g) 1 kilogram (kg) = 2.20 pounds (lb) 1 pound (lb) = 454 grams (g) Temperature 0F = 1.8 0C + 32 0C = (0F-32)/1.8 K = 0C + 273 Gases 1 atm = 760 mm Hg 1 mole (STP) = 22.4 L H2O density = 1.00 g/l mL melt = 80 cal/g boil = 540 cal/g SH = 1 cal/g C Energy 1 Cal = 1 kcal = 1000 cal 1 calorie (cal) = 4.18 joules (J) METRIC CONVERSION FACTORS Metric Relationship (Equality) Conversion Factors Length 1 m = 1,000 mm 1m           and        1000 mm   1000 mm                        1m 1 cm = 10 mm 1cm         and         10 mm     10 mm                         1cm Volume 1 L = 1,000 mL 1L           and        1000 mL   1000 mL                         1L 1 dL = 100 mL 1dL          and       1000 mL     100 mL                       1dL Mass 1 kg = 1,000 g 1kg          and        1000 g     1000 g                        1kg 1 g = 1,000 mg 1g            and        1000 mg   1000 mg                        1g METRIC-U.S. RELATIONSHIPS & CONVERSION FACTORS Relationship Conversion Factors Length 2.54 cm = 1 in. 2.54 cm        and           1 in.            1 in.                          2.54 cm 1 m = 39.4 in. 1m               and         39.4 in.     39.4 in.                             1m Volume 946 mL = 1 qt. 946 mL       and           _1 qt.  _         1 qt.                           946 mL 1 L = 1.06 qt. 1L               and          1.06 qt.      1.06 qt.                               1L Mass 454 g = 1 lb. 454 g           and          _1 lb.           1 lb.                             454 g 1 kg = 2.20 lb. 1 kg           and          2.20 lb.        2.20 lb                            1 kg    